Research Paper Advance Articles

Figure 5. Characterization of hypoxia-induced brain endothelial proliferation at different ages. (A) Frozen brain sections taken from mice of different ages (2–23 months) exposed to hypoxia (8% O₂) for 4 days were dual-stained for CD31 (AlexaFluor-488) and Ki67 (Cy-3). Images were captured in the midbrain. Scale bars = 100 μm. (B) Quantification of the density of CD31⁺/Ki67⁺ cells in the midbrain in different age mice following 4 days hypoxia. Results are expressed as the mean ± standard error of the mean (SEM) (n = 5 mice/group). ^*p < 0.05, ^**p < 0.01. One-way analysis of variance (ANOVA) followed by Tukey’s multiple comparison post-hoc test. Note that while endothelial proliferation was relatively constant across the age range, we observed a small but significant increase between 2–6 months and a small but significant decrease after 15 months.